JPH0781638B2 - Pneumatic cylinder with cushioning mechanism that can change stop position - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic cylinder with a cushioning mechanism capable of changing a stop position on the head side by an external signal.

[Prior Art] It is widely practiced to attach a work piece or a working tool thereof to a piston rod of a pneumatic cylinder to convey or work the work piece. In order to cope with the recent high-mix low-volume production, it is possible to reset the piston stop position of the pneumatic cylinder with a stop position accuracy of ± 0.1 to ± 0.05 mm according to the production process each time the workpiece is switched. It is done frequently.

For this reason, there is a strong demand for the practical application of a device that can accurately and quickly adjust the stop position of the piston in the pneumatic cylinder without using human hands.

In order to change the stop position of the cylinder as described above, conventionally, a method of providing a mechanical stopper whose position can be changed outside or inside the pneumatic cylinder has been widely used (for example, JP-A-58-142072). See the bulletin). In such a method, by using a buffer mechanism together, ± 0.
A stop position accuracy of about 05 mm is relatively easy to obtain, but because the piston rod is made hollow and a complicated mechanism is provided on the rod side or head side cover of the cylinder tube, it is a commonly used buffer. The structure makes it difficult to attach a mechanism.

Then, without the buffer mechanism, the piston may collide with the mechanical stopper at a high speed, and after it rebounds, it may stop at a position apart from the mechanical stopper due to friction.
Therefore, in order to improve the accuracy of the stop position of the piston, the buffer mechanism is practically indispensable.

In addition, the current position of the piston rod is constantly detected electrically, and the drive adjuster is operated by the operation signal obtained by calculating the error from the target position by the position adjuster,
A method of controlling the position of the piston rod is also generally used, but in order to improve the stop position accuracy, not only a relatively expensive position detector and control device are required, but also
When the piston is operated at a high speed, the accuracy of the stop position is lowered, so that a more expensive control device or the like is required.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to provide a pneumatic cylinder having a cushioning mechanism in which the stop position of the piston on the head side can be changed and which cushions the piston by containing air pressure. To do.

[Means for Solving the Problems] In order to solve the above problems, a pneumatic cylinder with a cushioning mechanism of the present invention is provided with a cylinder tube to which a fixed part is attached, a piston that slides in the cylinder tube, and an piston that is attached to the piston. A piston rod that hermetically penetrates a rod side cover that is integral with or separate from the cylinder tube, a head block that is hermetically disposed in the cylinder tube and that is positionally adjustable in the sliding direction of the piston, and a piston of the head block. The head having a screw rod provided on the opposite side to the sliding rod, a feed nut supported by a fixed portion and screwed into the screw rod, and a pulse motor for rotating the feed nut based on a signal from the outside. From the moving mechanism that moves the block to the required position in the sliding direction of the piston, and the pressure chamber defined by the piston It is characterized in that it comprises a buffer mechanism for temporarily containing the discharged air near the end of the stroke of the piston to stop the piston at the end of the stroke.

[Operation] When the position of the head block of the pneumatic cylinder is adjusted to the desired position by the moving mechanism and then the compressed air is supplied to and discharged from the cylinder, the piston has the same end position of the rod side stroke and the position of the head block. Driven within the required stroke range set by, the buffer mechanism stops by the containment air pressure at the end of the stroke.

In this case, there are no members on the rod side cover and the piston side of the head block that require a particularly large space other than the supply / discharge ports, so it is possible to provide a shock absorbing mechanism for them and thereby drive the piston at high speed. The buffer mechanism can be stopped at an accurate stop position in a buffer manner.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

The pneumatic cylinder according to the present invention makes it possible to change the piston stop position by an external signal, and particularly the head side stop position.

FIG. 1 shows an embodiment of a pneumatic cylinder according to the present invention. In FIG. 1, reference numeral 1 denotes a fixed portion to which the pneumatic cylinder is attached, which is usually constituted by a part of an appropriate device to which the pneumatic cylinder is attached. Is a cylinder tube fixed to the fixed portion 1, 3 is a piston that slides in the tube 2, 4 is a piston rod that airtightly penetrates the rod side cover 2a that is integral with or separate from the tube 2, and 5 is the above The head block is airtightly arranged in the tube 2 and is positionally adjustable in the sliding direction of the piston. In order to simplify the drawing, a buffer mechanism for stopping the piston 3 in a buffer manner is not shown.

The head block 5 is attached to the tip of a screw rod 6, the screw rod 6 penetrates the fixed portion 1 and is projected to the other side, and an end plate 7 attached to the tip of the screw rod 6 is parallel to the screw rod 6. Guide rods 8 and 8 are attached. Above guide rod
Numerals 8 and 8 are inserted into the fixed portion 1 and prevent rotation of the screw rod 6 when the screw rod 6 moves in the axial direction.

A feed nut 10 is screwed onto the screw rod 6. This feed nut 10 has a ball bearing 11,1 on the fixed part 1.
It is supported by 1, cannot move in the axial direction of the screw rod 6, and can rotate only. Further, a gear 12 is formed on the outer periphery of the feed nut 10, and the gear 12 meshes with a small gear 13 on a rotary shaft 15 of a pulse motor 14 attached to the fixed portion 1, and the screw rod 6 is provided. The moving mechanism 9 is composed of the feed nut 10, and the pulse motor 14 that rotates the feed nut 10.

Therefore, the rotation of the pulse motor 14 causes the small gear 13 and the gear to rotate.
When the feed nut is rotated via 12, the screw rod 6 moves in its axial direction, the head block 5 moves forward or backward in the cylinder tube 2, and the stop position of the piston 3 is designed.

If necessary, a braking brake may be installed on the shaft of the pulse motor 14 to prevent the stop position of the head block 5 from being displaced due to a collision of the piston or a load force.

The end plate 7 attached to the tip of the screw rod 6 has a protrusion 16 for setting the origin of the moving position of the head block 5.
An origin position detector 17 composed of a switch or the like is appropriately provided at a fixed portion so that the protrusion 16 generates an electric signal at the origin of the moving position of the head block 5.
The protrusion 16 can be attached not only to the end plate 7 but also to, for example, the guide rods 8, 8 parallel to the screw rod 6.

The position detection accuracy of the origin position detector is important because it is directly related to the stop position accuracy of the piston 3 and needs to be highly accurate. Specifically, the movement amount corresponding to one step of the pulse motor (for example, 0.05 mm or less)
It is desirable to have detection accuracy, which is the same as that of the above-mentioned protrusion 16
Has entered both regions near the origin (for example, response difference 1
(2 mm limit switch detection signal) and a specific tooth position detection signal of the gear 12 on the outer periphery of the feed nut 10 screwed to the screw rod 6 (signal by opening and closing a photoelectric switch by a small hole provided at the base of the tooth) It is possible to easily and highly accurately detect it by a method such as a combination with, but it is possible to use other suitable configurations.

Pressure air for driving the piston 3 is supplied to and discharged from the pressure chambers 18 and 19 on both sides of the piston 3 through pressure air supply and discharge ports 21 and 22. In this case, supply / discharge port on the rod side
21 is provided on the cover 2a immediately on the rod, and the head side supply / discharge port 22 is provided on the head block 5.

Thus, since the cover 2a and the head block 5 are not provided with members other than the supply / discharge ports 21 and 22, which require a relatively large space, such as members for setting the stop position of the piston, A cushioning mechanism that cushions the piston by containment air pressure, as described below,
They are provided on the cover 2a and the head block 5.

The buffer mechanism is generally used in a pneumatic cylinder, and an example thereof is shown in FIG. The empty pressurizing cylinder shown in the figure shows a case where the buffer mechanism 24 is provided at both ends of the cylinder tube 2 on the rod side and the head side, and a cover attached to the rod side end of the cylinder tube 2.
2a and the head block 5 are provided with recessed holes 25 and 26 in the axial direction which also serve as flow paths for the pressure air, and cushion packings 27 and 28 are attached to the inner peripheral surfaces of the recessed holes 25 and 26 to slide the cylinder tube 2 inside. While being fitted into the recessed holes 25, 26 at the stroke end of the movable piston 3, the cushion packing 27,
Cushion rings 29 and 30 that are in sliding contact with 28 are attached.
Further, the pressure chambers 18 and 19 on both sides of the piston 3 and the feed and discharge ports 21 and 22 on the rod side and the head side are needle valves whose opening degree can be adjusted separately from the flow paths passing through the recessed holes 25 and 26. 33,3
The bypass flow paths 31 and 32 having 4 are connected to each other.

Therefore, when the piston 3 approaches the stroke end on the rod side, for example, the tip of the cushion ring 29 fits into the cushion packing 27, the internal pressure of the cylinder rises, and the piston is decelerated.

The drive pulse signal of the pulse motor 14 described above can be generated by an appropriate means. FIG. 3 shows an example of the signal generator.

In this signal generation unit, the signal conversion unit receives a piston stop position signal to be changed from a host computer or the like, and a step of the pulse motor corresponding to the distance between the set point for stopping the head block 5 and the origin. Calculate the number and set it in the first counter. If the number of pulses corresponding to the above-mentioned number of steps is given as a signal from the host device, only the first counter need be provided.

On the other hand, the signal generator is provided with a second counter (addition / subtraction) which is reset by receiving the output signal of the origin position detector 17. This second counter counts and records the number of output pulses to the pulse motor 14 (the number of steps of the pulse motor), and the count number is compared with the count number of the first counter in the comparison control unit, The forward or backward drive pulse signal is output until the difference between the two count numbers becomes 0 corresponding to the positive or negative. In the second count, the forward pulse number is added and the backward pulse number is subtracted.

With such a configuration, the signal generator outputs the number of pulses corresponding to the position signal from the host device to the pulse motor 14.

If a drive signal is further sent to the pulse motor 14 when the head block 5 reaches the limit point for forward or reverse movement, the pulse motor may be damaged. It would be necessary to provide a limit switch for each of them, input these open / close signals to the drive signal generator, and stop the further output of the forward or reverse signals. Further, a torque limiter may be provided on the rotary shaft 15 of the pulse motor 14 to stop the output of the drive signal generator when the load on the pulse motor increases abnormally.

Further, when the above-mentioned braking brake is required for the rotating shaft 15 of the pulse motor 14, a function for controlling the braking brake in cooperation with the output of the drive signal is required.

In the pneumatic cylinder having the above configuration, it is assumed that the head block is stopped at the origin position when the drive is started.
This head block may be manually moved to the origin position, but it is also easy to incorporate a sequencer into the signal generating unit to perform an automatic origin returning operation. In any case, the second counter of the signal generator is reset by the origin position signal.

When the stop position signal is updated by a host device such as a computer and a forward signal is output from the signal generator, the pulse motor rotates in steps by a predetermined number of pulses. As a result, the feed nut 10 screwed into the screw rod 6 rotates corresponding to the gear ratio of the small gear 13 and the gear 12, the head block starts moving forward, and the pulse motor stops when the drive signal stops.
That is, the head block stops at a position corresponding to the number of pulses input to the pulse motor from the origin with an accuracy equivalent to one step of the pulse motor.

When the position of the head block of the pneumatic cylinder is adjusted in this way, the piston is driven within the required range by the supply and discharge of the pressurized air from the supply / discharge port to the pressure chamber of the cylinder, and the rod side cover of the cylinder tube and the head block. By additionally providing the buffer mechanism 24, the piston can be stopped at an accurate stop position in a buffer manner while being driven at high speed.

[Effect of the Invention] The pneumatic cylinder of the present invention is a moving mechanism having a screw rod, a feed nut, and a pulse motor, and by moving the head block to a set position, the piston can be driven with a desired stroke. Since it is not necessary to use an expensive device for controlling the position of the piston like the pneumatic servo mechanism, the structure can be made simple and inexpensive.

Further, by the moving mechanism having the above-described structure, the rod side cover and the head block, which have space, are provided with the cushioning mechanism of the piston by the air pressure that is contained, so that the accuracy of the stop position of the piston can be improved.

Further, since the stroke of the piston is adjusted by moving the head block, the stroke can be adjusted when the stroke end position of the piston is constant.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of a pneumatic cylinder according to the present invention, FIG. 2 is a sectional view of a buffer mechanism for stopping a piston in a buffer manner, and FIG. 3 is a pulse motor in the pneumatic cylinder. FIG. 3 is a block configuration diagram of a signal generator that generates a drive pulse signal. 1 ... Fixed part, 2 ... Cylinder tube, 2a ... Rod side cover, 3 ... Piston, 4 ... Piston rod, 5 ... Head block, 6 ... Screw rod, 10 ... Feed nut, 14 ... … Pulse motor, 24 …… Buffer mechanism.

Claims (1)

[Claims] 1. A cylinder tube 2 to which a fixed portion 1 is attached, a piston 3 sliding in the cylinder tube 2, and a cylinder tube 2 attached to the piston 3.
A piston rod 4 that airtightly penetrates a rod side cover 2a that is integral with or separate from the rod cover 2; a head block 5 that is airtightly arranged in the cylinder tube 2 and is positionally adjustable in the sliding direction of the piston 3; Piston 3 of block 5
Screw rod 6 and fixed part 1 provided on the opposite side to the sliding direction
Has a feed nut 10 supported by the screw rod 6 and screwed to the screw rod 6, and a pulse motor 14 for rotating the feed nut 10 based on a signal from the outside. The air discharged from the pressure chambers 18 and 19 defined by the piston 3 and the moving mechanism 9 that is moved to the vicinity of the stroke end of the piston 3 is temporarily contained, and the piston 3 is buffered to the end of the stroke. A pneumatic cylinder with a cushioning mechanism whose stop position can be changed, comprising: a cushioning mechanism 24, 24.